1. Field of the Invention
The present invention relates to an electronic pedometer for measuring the number of steps taken, by detecting walking of a human being or the like.
2. Description of the Prior Art
Heretofore, there has been developed an electronic pedometer for measuring the number of steps taken of a user by detecting walking of the user using a walk sensor.
In an electronic pedometer, for example, an acceleration sensor is used as a walk sensor. There are known an electronic pedometer using a system (direct carrying system) in which at least the acceleration sensor is directly worn in a body of a user such as the wrist or an arm to be carried with the user, an electronic pedometer using a system (indirect carrying system) in which at least the acceleration sensor is held in a pocket of a user's clothing, or a bag or the like of the user to be carried by the user, and the like (refer to Patent Documents 1 and 2, for example).
In particular, in the electronic pedometer using the indirect carrying system, there is no telling when a signal on the number of steps taken will be detected in many cases. Hence, a power supply usually supplies an electric power to an amplification circuit for amplifying a signal from the acceleration sensor to cause the amplification, whereby the amplification circuit is usually in an operation state. For example, not only when a user is sleeping, but when the acceleration sensor is left being held in a bag or the like, the amplification circuit is kept in the operation state, leading to a problem in that the electronic pedometer consumes much electric power. In addition, since the electronic pedometer is of a portable type, a battery is used as a power supply. Hence, there is encountered a problem in that a battery life is shortened and thus a battery must be frequently exchanged for a new one since the electronic pedometer consumes much electric power. Also, when the battery is a secondary battery, a problem occurs in that the secondary battery must be frequently charged with electricity.
In addition, in the case as well of the electronic pedometer using the direct carrying system, such as a watch type electronic pedometer, there is a problem in that when an electric power is continued to be supplied to the amplification circuit in a state in which the electronic pedometer is placed in a predetermined position during sleep, a rest or the like, electric power is wastefully consumed.
For a method of solving the above problems, as in a pedometer described in Patent Document 2, there is a conceivable method of changing a sampling frequency in correspondence to detection and non-detection of walk vibration. However, this method involves a problem in that when the sampling frequency is low, measurement precision is degraded.
<Patent Document 1> JP 09-223214 A
<Patent Document 2> JP 2001-143048 A
The present invention has been made in order to solve the above problems, and it is, therefore, an object of the present invention to provide an electronic pedometer which is capable of lengthening a battery life by saving power consumption without degrading measurement precision. It is another object of the present invention to provide an electronic pedometer which is capable of reducing the number of times of battery exchange or battery charge by lengthening a battery life without degrading measurement precision to save labor required for the battery exchange or battery charge.